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Development and Study of the Multi Pixel Photon Counter. Satoru Uozumi (Shinshu University, Japan) for the KEK Detector Technology Project / Photon Sensor Group Vienna Conference on Instrumentation 2007, Feb 19-24 , 2007. Introduction Fundamental Performance
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Development and Study of the Multi Pixel Photon Counter Satoru Uozumi (Shinshu University, Japan) for the KEK Detector Technology Project / Photon Sensor Group Vienna Conference on Instrumentation 2007, Feb 19-24 , 2007 • Introduction • Fundamental Performance • Application to High Energy Physics • Summary
KEK Detector Technology ProjectPhoton Sensor Group(http://rd.kek.jp/)(KEK, Kobe, Kyoto, Nagoya, Nara-WU, NDA, Niigata, Shinshu, Tokyo/ICEPP, Tsukuba) S. Gomi, H. Hano,T. Iijima, S. Itoh, K. Kawagoe, S. H. Kim, T. Kubota, T. Maeda, T. Matsumura, Y. Mazuka, K. Miyabayashi, T. Murakami, T. Nakadaira, T. Nakaya, H. Otono, E. Sano, T. Shinkawa, Y. Sudo, T. Takeshita, M. Taguchi, T. Tsubokawa, S. Uozumi, M. Yamaoka, H. Yamazaki, M. Yokoyama, K. Yoshimura, T. Yoshioka And special thanks to Hamamatsu photonics K.K.
The Multi Pixel Photon Counter (MPPC)- A silicon avalanche photo-diode with multi-pixel structure - 1 mm Si Resistor Vbias Guard ring n- p+ n+ p- Substrate • Each pixel works as a Geiger-mode APD, • One pixel can count only one photon. • g need multi - pixel structure for photon counting • Electric charges from all the fired pixels are summed up • and read out as a signal. • There are 4 different types available: substrate p+ 400 pixel 50mm 1600 pixel
Excellent Photon Counting Ability 0,1,2,3,4,5,6,7, . . photoelectrons ! 1600 pixel 1600 pixel 1 photoelectron 2 photoelectrons
Fundamental performance • Gain • Dark Noise Rate • Inter-pixel Cross-talk • Photon Detection Efficiency • Uniformity in a pixel
30oC • 25oC • 20oC • 15oC • 10oC • 0oC • -20oC Fundamental Performance - Gain Gain =106 • 25oC • 20oC • 15oC 1600 pixel Gain = 106 Over-voltage • C … Pixel capacity • V0 … Breakdown voltage • 25oC • 20oC • 15oC • V0 temperature (DV0/DT ~ 50 mV/Co) • Larger pixel size results in larger gain.
Variation of V0 and C over 750 MPPCs (Measured at 15oC) Variation ~ 0.45 V Variation < 4% • ~750 pieces of 1600 pixel MPPCs have been tested. • Device-by-device variation is less than a few %. • g No need for further selection or categorization on massive use ! • Just need a small tuning of operation voltages.
Fundamental Performance – Dark Noise Rate • 30 oC • 25 oC • 20 oC • 15 oC • 10 oC • 0 oC • -20 oC 1600 pixel 300 kHz 300 kHz • 25 oC • 20 oC • 15 oC • The dark noise is caused • by thermal electrons. • Its rate depends on both • over-voltage and temperature. • More number of pixels • g smaller active area • g fewer noise rate 300 kHz
Inter-pixel cross-talk is caused by a photon created in an avalanche Probability of the cross-talk has been measured using dark noise rates: Fundamental Performance- Inter-pixel Cross-talk - • 25 oC • 20 oC • 15 oC • 30 oC • 25 oC • 20 oC • 15 oC • 10 oC • 0 oC • -20 oC 1600 pixel • 25 oC • 20 oC • 15 oC • Cross-talk probability is affected by over-voltage, but not affected by temperature.
Fundamental Performance- Photon Detection Efficiency (P.D.E) - • Q.E. (~ 0.9) … Quantum Efficiency • eGeiger(~ up to 0.9 , depends on bias voltage) … Probability to cause avalanche • egeom(0.25 ~ 0.65 , depends on pixel size) … Fraction of sensitive region in a sensor Measurement of relative P.D.E. • Inject same light pulse into both the MPPC and the PMT, and compare light yield measured by both: LED (l=450~550nm) MPPC ~15 % PMT hole
Fundamental Performance– Photon Detection Efficiency - 2 1600 pixel • 25oC • 20oC • 15oC 1 1 2 • PDE of the MPPC is x1~2 of the PMT ! • Larger pixel size • g less dead space • g larger PDE • The PDE also depends on over-voltage, • and slightly affected by temperature • change. • 25oC • 20oC • 15oC 1
1600 pixel Microscopic view Laser Scan in One Pixel • Pin-point scan has been done using YAG laser • (l = 532 nm) with spot size ~ 1 mm. • Variation of photon sensitivity and gain in one pixel • are evaluated. • Observed variation is 2 ~ 5 % in a sensitive area • for the 100 / 400 / 1600 pixel MPPCs. 1600 pixel Sensitivity 1600 pixel Gain Gain (x 105) y-point (1mm pitch) Sensitivity (arbitrary) y-point (2mm pitch) One pixel Variation ~ 3 % x-point (2mm pitch) x-point (1mm pitch)
Application to High Energy Physics- Calorimeter for linear collider experiment - Light yield of scintillator strip (1 x 4.5 x 0.2 cm) for beta-ray WLS fiber readout Direct readout MPPC MPPC Light yield ~ 21 p.e. Light yield ~ 13 p.e. Light yield (ADC counts) • The MPPC is feasible for strip-type • scintillator calorimeter. • (size,cost, performance…) • Dynamic range is the key issue. • First scintillator-ECAL beam test • will start in next week at DESY !
Application to High Energy Physics- T2K near detectors - OffAxis detector OnAxis detector Scintillator + WLS fiber With MPPC readout • Need to read out large number of • signals from WLS fibers in limited space • Used in 0.2 Tesla magnetic field • The MPPC is the perfect solution ! - Belle Ring Imaging Cerenkov Detector - • Capture Cerenkov ring image for particle ID • For the ring imaging, • Sufficient photon detection efficiency • Position resolution (~5 mm) • are required for photon sensor. • MPPC is a powerful candidate for this purpose, • Larger sensor area (~3x3 mm2) is desired • in future development. Aerogel radiators
The MPPC is still evolving … Stay tuned for future development ! Near future • Improved performance • Larger sensor area • More pixels Jan. 2006 • 100/400/1600 pixels • Larger PDE • More pixels 2006-2007 • 100/400/1600 pixels commercialized • Improved Gain and dark noise • Tests of massive use Mar. 2005 • 100/400 pixels • First sample from Hamamatsu ?
Summary • The MPPC is a promising photon sensor which has many remarkable features. • High gain, compact size, low-cost, excellent P.D.E., etc …. • Extensive R&D of the MPPC is ongoing in KEK DTP group collaborating with Hamamatsu photonics. • Study and improvement of basic properties … underway • Evaluation of variation over many samples … underway • Study radiation hardness (for g-ray, neutron) … just started • Evaluate robustness and long-term stability … start soon • Test magnetic-field tolerance … near future • Tests for actual use at several high energy physics experiments are also underway. • Applications in various other fields are being explored. • Positron Emission Tomography, etc… • The improvement of the performance will be continued toward the “Perfect Photon Sensor” !
Novel Photon Detector WorkshopJune-2007 Kobe, Japan The KEK Detector Technology Project group will host an international workshop for the future photon sensors. Check the KEKDTP web site: http://rd.kek.jp/ Contact : Takeshi.Nakadaira@kek.jp
Application to Other Fields • Positron Emission Tomography (PET) • … a powerful method to detect cancer activity. • Capture gamma pair and identify position of the cancer. • Spatial resolution is greatly improved by • finer granularity (~1 mm of crystal block size). • MPPC is ideal to read out each individual crystal blocks.
MPPCs on sale (Numbers from HPK catalog) • Hamamatsu photonics is starting to deliver the MPPC. • See following page for more information: http://www.hamamatsu.com/news/2006/2006_10_26.html